Atopy patch test reactions are associated with T lymphocyte-mediated allergen-specific immune responses in atopic dermatitis

Background Positive test reactions to epicutaneous application of aeroaller gens served as a model of 'early' eczema in atopic dermatitis (AD) in a num ber of dermato -immunological studies. However, no quantitative evaluation has been performed so far comparing specific T-cell activation parameters i n the peripheral blood of AD patients with positive or negative atopy patch tests (APT). Objective The purpose of this study was to investigate specific immunologic al parameters in patients with atopic dermatitis showing positive or negati ve atopy patch tests reactions. Methods APT results (n = 96) were compared with allergen-specific IEE, specific lymphocyte proliferation, and the expr ession of 'activation' markers on peripheral blood T-cells upon in vitro st imulation with house dust mite, cat or grass pollen allergens. Results Only a subpopulation (48%) of patients sensitized to aeroallergens (i.e. specific IgE >0.7kU/L) developed APT-reactions to the corresponding a llergen. APT reactions were, however, significantly associated with allerge n specific lymphocyte proliferation (p<0.0001), and a higher number of CD54 (+) or CD30(+) T-cells (p<0.05) upon in vitro stimulation. Conclusion The association of delayed skin reactions with allergen specific T-cell parameters in the blood points to an immunologically mediated mecha nism leading to positive reactions in the APT.